Method of restoring a tooth

ABSTRACT

A method of restoring a tooth is provided. method comprises the steps of dispensing a curable composition from an applicator and curing the curable composition. The applicator has a needle with a lumen The composition is injected into a hollow on the tooth to achieve a desired shape. The composition includes curable liquid resin portion and an inorganic filler portion. The curable liquid resin portion has a polymerizable binder resin.

FIELD OF THE INVENTION

[0001] The present invention relates to a method for restoring a defectin a tooth by using a curable composite material.

BACKGROUND

[0002] Teeth with dental decays such as cavities are generally restoredby removing the decayed area and applying a restorative thereon.Traditionally, amalgam material has been used for filling and repairingteeth. Because the amalgam material tends to harden as it is beingworked, and its thick, lumpy consistency necessitates using specializedtools for pushing the materials into corners and crevices to facilitateadaptation to the tooth, its use is inconvenient and causes greatdiscomfort to the patient. Moreover, the retention of an amalgamresotative in a tooth is by bulk. For repairing a small decayed area,often an amount of healthy tool structure many times the decayed areahas to be removed to provide toom to receive the amalgam material.

[0003] The concern of the presence of mercury in amalgam material hasled to the introduction of other restoratives that do not containmercury. For example, “Universal Paste” composites, such as P-SO andZ-100 sold by 3M Company, have been used for restoring teeth. Examplesof other composite materials that can be used for repairing teethinclude the compositions disclosed in U.S. Pat. No. 4,553,940 (Koblritz,et al) and U.S. Pat. No. 5,228,907 (Eppinger, et al).

[0004] Generally, composite materials for repairing teeth are thick andsticky, making them difficult to work with and highly technical skill isrequired of the operator to properly place such materials in teeth forrestoration purposes. Universal paste type composites are generally usedby trowelling an amount of the paste into position in a hollow (or voidor cavity), tamping the paste down to improve contact with the surfaceof the cavity, carving the excessive paste into a rough outline of thedesired shape, and polishing the cured composite to a desired shape andsmoothness.

[0005] Because a composite material, similar to amalgam material, isgenerally applied as a lump in the prepared location in a tooth, voidsand porosities are often incorporated into the material during placementbecause of the difficulty in manipulating the material into corners andcrevices in the tooth. Furthermore, if a composite material is lightcurable, because of the thickness of the composite material applied,incomplete polymerization often results.

[0006] Another kind of restorative material that does not containmercury is a film-forming composition that is generally used as asealant, glaze, or adhesive. Typically, such a film-forming dentalcomposition contains resins with little or no filler materials. Suchfilmforming dental compositions are typically used for sealing the toothagainst cracks adjacent to fillings. Such compositions generally havelow viscosity and can be applied to the tooth by using a brush. Anexample of a sealant is disclosed in U.S. Pat. No. 4,001,483 (Lee, Jr.,et al.). Such a composition is generally applied as a thin coating andwhen cured, forms a sealing coat on the tooth. Yet another kind ofcoating composite is used for masking stains and discolorations. Forexample, U.S. Pat. No. 4,150,485 (Lee, Jr., et al) discloses a brushedon dental restorative coating composition used for covering surfaceimperfections. This composition has a higher viscosity than conventionalsealants. Such film-forming and coating compositions have not beenapplied in restoration of tooth decays such as filling cavities.

SUMMARY

[0007] The present invention provides a method of restoring a tooth thathas a defect. The method includes dispensing a curable compositionthrough a needle with a lumen into a hollow on the tooth to achieve adesired shape and curing the curable composition. As used herein, theterm “needle” refers to a slender, hollow, stiff instrument which may bestraight, curved or bent, with or without a sharp point. The compositioncontains a curable liquid resin portion and an inorganic filler portion.The curable liquid resin portion has a polymerizable binder resin. Asused herein, a “hollow” refers to a void area or cavity that resultsafter a tooth has been prepared to receive a restorative by a cutting orabrasive tool such as a dental bur.

[0008] In another aspect, the present invention provides a method ofrestoring a tooth having a decayed portion including the steps ofremoving the decayed portion to form a hollow in the tooth, coating thesurface in the hollow with a curable bond and curing the bond,dispensing a curable composition from a needle in the hollow to achievea desired shape, curing the curable composition, and repeating thedispensing of the curable composition and curing the curable compositionuntil a cured structure of desired shape and smoothness is obtained. Inremoving the decayed portion, an amount of an adjacent healthy portionor the tooth is removed with the decayed portion. The volume of thehealthy portion removed is about zero to three times, preferably 0.5 to3 times the decayed portion. The composition contains a curable liquidresin portion and an inorganic filler portion. The curable liquidportion has a polymerizable binder resin and a polymerizable diluentmonomer less viscous than the polymerizable binder resin.

[0009] The present invention provides yet another method for restoring atooth using a composition that contains a curable liquid resin portionand an inorganic filler portion. The method includes the steps ofdispensing a curable composition from a needle as one of a layer and adrop in the hollow, curing the curable composition wherein the one of alayer and drop shrinks when it is cured, dispensing the curablecomposition as one of a layer and drop on top of the cured compositionand in the void space resulted from the shrinkage to compensate for theshrinkage, and repeating the dispensing and curing of the composition inthe hollow until a cured structure of desired shape and smoothness isobtained.

[0010] The method of the present invention can be advantageouslyutilized to restore defects in teeth. Because of the composition of thepresent invention can be applied using a hypodermic needle like tubularstructure, the composition can be applied into a small hollow in hardto-reach places on a tooth. By laying the curable composition as a thinlayer or small drop, substantially complete curing by light (as comparedto relatively incomplete curing when conventional universal paste-typeof composite is used) can be realized. Such substantial complete curingleads to improved mechanical integrity and chemical resistance of therestorative material in the tooth. Better curing leads to less stresscracking taking place in the restorative material.

[0011] The use of conventional composite material often leads to a greatamount of shrinkage as the material is cured. Such shrinkage can lead tomany problems, such as accelerated wear, open margins between the toothsurface and the filling material, leakage of foreign material into theunfilled area, thereby causing degradation and subsequent development ofcaries. In the present invention, by depositing the composition as thinlayers, curing, and repeating the process the void area left by theshrinkage of a previous cured area can be filled with a subsequent layerwith the composition, thereby eliminating or greatly reducing thepresence of unfilled areas caused by shrinkage.

[0012] The thixotropic characteristic of the restorative curablecomposition of the present invention greatly facilitates the restorationof tooth without having to shape the composition using a scraping tool.The thixotropic substance can be forced through a syringe and needle andcarefully deposited in a desired location and cured. By graduallybuilding up the cured structure, there is no need to remove excesscomposite material to achieve a desired shape. The relatively lowviscosity of the composition helps to spread the composition intocrevices and corners to greatly reduced amount of void area so that astrong bond can result between the composition and the tooth withoutdepending on retention of the restorative material by bulk. The lowviscosity nature of the composition, as compared to conventionaluniversal paste type composites, allows for much less manipulation ofeach increment placement of the composition. Therefore, manipulation bypaddling, pushing or prodding to place and shape the composite material(as in the case of using a universal paste) is not necessary. This makesthe composition of the present invention easier and quicker to place andresults in a less degree of discomfort to the patient. Because of theaffinity of the bond to the composition of the present invention, thecomposition is further facilitated to flow into crevices and cornersit—encounters. A drop (i.e., a dab or a bead) or a thin layer of thecomposition, when placed in a hollow, such as for Class IV restoration,will not run (i.e., flow or drip out of the hollow under gravity). Thesurface tension of the thixotropic composition is selected by varyingthe concentration of the various ingredients in the composition so as tobecome compatible with the surface of the tooth structure and to providean affinity to the bond.

[0013] The curing of the composition of the present invention provides asmooth surface, thereby eliminating the need for finishing, polishing,and visual inspection of margins. This, and the ability to adhere to asurface of the tooth without depending on bulk, make possible therestoration of a tooth without removing an excess amount of healthytooth structure as in a case of using amalgam or conventional universalpaste-type composite. This affords a great advantage of retaining asignificant amount of the healthy tooth structure, thereby reducing atrauma to the tooth and the likelihood of losing the tooth completelythrough multiple restorative procedures. Contrarily, the prior artmethods requires excessive removal of healthy tooth structure. Quiteoften, because of wear (i.e., abrasion) and bacterial attack through theyears, the same tooth needs to be restored many time. With excessivetooth structure removal as in the prior art methods, the tooth may beweakened to the extent that a crown or extraction is required. Themethod of present invention, being much more conservative in toothstructure removal, greatly reduces the need for such crowns andextractions.

[0014] Because no polishing is necessary to smooth the surface of therestorative structure, polishing-induced cracks, fissures, orirregularities are absent on the restorative structure. Such crevices,fissures and irregularities, if present, would increase the porosity ofthe restorative structure and lead to accelerated degradation and wear.Mechanical polishing results in scratches on the polished surface. Suchscratches, even the finest ones, increase the surface area formechanical and chemical degradation. Such scratches violate the bondingbetween the affected filler particles and the resin, which eventuallylead to the filler particles falling off. The present invention avoidssuch scratches, resulting in a longer lasting restoration on the tooth.

[0015] In the present method, a syringe-type applicator can be used tostore and deliver the composition through a needle-type tubularstructure to a desired location on the tooth. Therefore, only oneinstrument (e.g., the applicator with a needle) is needed for deliveringand shaping the composition. No separate instruments are needed forperforming the storage, delivery and shaping procedures. A single dropof the composition can be placed precisely on a desired location, beads(or drops) of the composition can be deposited in a line in a verticalor horizontal direction, and a large area can be covered with a thinlayer of the composition by using the syringe with a needle. Using suchan applicator, the surface of a layer of the composition can be strokedin a brush-like fashion to spread out or be teased into a peak. Becauseof the thixotropic nature of the composition, various shapes can beaccomplished by manipulating the composition with the tip of the needle.Such ease of manipulation affords great convenience to the operator inshaping the composition. Alternatively, a desired shape can be achievedby depositing the composition in small increments to build up the curedrestorative structure.

[0016] Building the restorative structure this way obviate the need topaddle, push or prod the filling material in the hollow as with theprior art method. This further reduces the trauma and discomfort to thepatient. Furthermore, because the restorative structure is built inincrements and requires less force, the operator (i.e., dentist) hasmuch better control. The method of the present invention, because of itsease of use and not requiring polishing, can also be done faster thanprior art methods using amalgam material or universal paste.

[0017] By utilizing the method of the present invention, certain typesof tooth restoration that have been very difficult to perform can bedone relatively easily. For example, a Class IV restoration (See examplebelow) requires the building of tools in the corner of the tooth.Amalgam generally cannot be used for this procedure. Traditional type ofpaste composite, although can be used, are very difficult to place andform into a desired geometry. When conventional methods are used, voidsand porosities often occur and require additional material to coverthem. For Class V restorations, amalgam application requires extraretention and undercuts, necessitating excessive tooth structure removaland weakening of the tooth. The use of conventional universal pastecomposite aces similar problems. Utilizing the method of the presentinvention, restoration by simply laying the composition at the preciselocation one layer or one bead at a time and curing renders theprocedure relatively easy to perform and result in a structurally sturdyand aesthetically appealing restored tooth.

BRIEF DESCRIPTION OF THE DRAWING

[0018] Illustrative embodiments of the invention are shown in thevarious figures. Throughout the figures, which are not drawn to scale toshow details, identical reference numerals refer to identical structuralelements, wherein:

[0019]FIG. 1 shows a cross-sectional view of a tooth showing a hollowbeing restored using a syringe and needle in an embodiment of the methodof the present invention;

[0020]FIG. 2 is a cross-sectional view of a tooth showing a hollow beingrestored with a further step of the embodiment of the method of FIG. 1;

[0021]FIG. 3 is a cross-sectional view of a tooth after restoration withthe embodiment of the method of FIG. 1;

[0022]FIG. 4 is a schematic top view of a tooth after a Class I sealantrestoration;

[0023]FIG. 5 is a schematic top view of a tooth after a Class I fillingrestoration;

[0024]FIG. 6 is a schematic cross-sectional view of a tooth after aClass II filling restoration;

[0025]FIG. 7 is a schematic front view of a tooth after a Class IIIfilling restoration;

[0026]FIG. 8 is a schematic front view of a tooth after a Class IVfilling restoration; and

[0027]FIG. 9 is a schematic cross-sectional view of a portion of a toothafter a Class V filling restoration.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention utilizes a composition for the restorationof teeth, such as dental fillings for the repair of dental caries.

[0029] The Composition

[0030] The composition applicable in the present invention includes acurable liquid resin portion containing one or more binder resins and aninorganic filler portion having inorganic fillers. Optional ingredientsthat can be included in the composition of the present application caninclude pigments, opacifiers and the like, for, improving the aestheticappearance of the composition after polymerization.

[0031] Binder resins are provided in the composition of the presentapplication for binding the various ingredients, including the inorganicfillers so that after polymerization, the composition forms a solid,rigid, mechanically sturdy material effective for sustaining mechanicaland chemical challenges which are normally encountered by theload-bearing surface of a tooth. Binder resins suitable for such anapplication include ethylenically unsaturated polymerizable materials.Preferably, the resin is an acrylated polyester. Such a material may bea monomer, dimer, trimer, and the like that is polymerizable. Apreferred material is 2,2-bis [4(2hydroxy-3-methacryloxypropoxy)phenyl]propane (hereinafter abbreviated as bis-GMA). Another materialapplicable is polyurethane dimethacrylate (PUDMA). A person skilled inthe art would understand that derivatives and polymers and combinationsof the above-described materials as well as other materials with similarchemical and physical properties may be utilized as the binder resin inthe composition of the present application.

[0032] Preferably, the composition applicable in the present inventionalso includes one or more diluent monomers in an amount effective torender the viscosity of the liquid resin portion (which includes thebinder resins and the diluent monomers) low enough to be mixed with theinorganic fillers to provide an injectable composition through a syringeneedle. Preferably, the diluent monomer can be mixed with the binderresin to have a Brookfield viscosity of less than 6,000 centipoises(cps) at 25°, more preferably between about 500 and 5,000 cps, morepreferably between about 1,000 and 5,000 cps, even more preferablybetween about 1,000 and 3,000 cps.

[0033] The diluent monomer applicable in the present application ispolymerizable. Preferably, the diluent monomers are acrylic materialssuch as 2hydroxyethylmethacrylate (HEMA), ethylene glycoldimethacrylate, diethyleneglycol dimethacrylate, triethylene glycoldimethyacrylate (TEGDMA), trimethylo propane trimethyacrylate, analogousacrylate, and the like. The more preferred diluent monomers are HEMA andTEGDMA.

[0034] Other polymerizable material that can be used as monomer orprepolymers to result in a curable liquid portion of appropriateviscosity include methyl methacrylate and bisphenol A dimethacrylate. Itis to be understood that a person skilled in the art will be able todevice a curable liquid resin portion based on the present disclosure byusing the above-described or other ingredients. It is believed that acomposition can be made with one or more resins that have a viscosity inthe range applicable for syringe injection as disclosed in the presentdisclosure such that the one or more resins can be considered as thebinder resin or as the diluent.

[0035] The composition of the present invention also contains a catalystor initiator for initiating the polymerization of the binder resin andthe diluent monomer. Preferably, the polymerization of the compositionof the present invention in initiated by a initiator system having twocomponents, an alpha diketone photosensitive species and an aminereducing agent. Examples of suitable alpha diketones for initiatingpolymerization of the composition include camphoroquinone, benzil,biacetyl, 9,10phenanthrenequinone, and naphthoquinone. Of these, thenon-aromatic alpha diketones are preferred, camphoroquinone is the mostpreferred.

[0036] A combination of an amine reducing agent with the alpha diketoneresults in a visible light sensitizing system which is applicable in thecomposition of the present invention. Amines effective for use in suchvisible light sensitizing systems include tributylamine, tripropylamine,N-alkyldialkanolamine, tryalkanolamine and acrylate derivatives such asdimethylamino ethylmethacrylate. A preferred amine is methyldiethanolamine. The use of initiators for visible light sensitizingsystems in polymerization of tooth restorative composites is known inthe art. Further, a person skilled in the art will appreciate that basedon the present disclosure, many other binder resins, diluent monomers,alpha diketones, and amines having similar chemical and physicalproperties as those disclosed above may be utilized in the compositionof the present invention.

[0037] As previously stated, inorganic fillers are included in thecomposition of the present invention to impart hardness and durabilityto the polymerized product. Examples of inorganic fillers suitable forapplication in the composition of the present invention include bariumaluminum silicate, lithium aluminum silicate, strontium, lanthanum,tantalum, glass, silica, quartz, and the like. Preferably, the inorganicfillers are silanated (or silanized) to facilitate bonding with thebinder resins. Other suitable inorganic fillers include alumina,zirconia, tin oxide, and titania.

[0038] Preferably, the inorganic fillers have a particle sizedistribution effective for resulting in a cured product having a surfacethat is smooth compared to surfaces that have been polished byconventional dental restoration technology. Generally particle sizeranging from about 0.005 to 15 microns is applicable. Preferredinorganic fillers have a particle size of about 0.01 to 5 microns. Theparticle size of the inorganic fillers is selected so that the inorganicloading in the compensation is effective to produce a cured product ofdesired strength, hardness and durability. Inorganic fillers of varioustypes and sizes can be combined (i.e. mixed) to result in a thixotropiccomposition injectable through a needle.

[0039] An inorganic filler that is particularly preferred is fumedsilica, which is a colloidal form of silica. Fumed silica generally hasa maximum particle size of about 0.05 micron. Although the applicationof the present invention is not limited by any theory, it is believedthat the electron distribution around the colloidal silica facilitatesthe formation of hydrogen bonding, thereby resulting in a network ofloosely attached particles when the colloidal silica is in anappropriate liquid. Therefore, a composition of the present inventioncontaining colloidal silica forms a thixotropic composition. Because ofthe hydrogen bonding, such a composition is relatively rigid (i.e.,viscous). When a stress is introduced into the composition, such as byshearing, the network is broken up partially, resulting in a lessviscous composition. The thixotropic characteristic of the compositionrenders it very useful for application in tooth restoration. Thecomposition can be injected through a long, thin needle such as ahypodermic needle because when pressure is applied by a syringe plungerto force the composition through the needle, the composition becomesless viscous and is dispensed through the exit opening of the needle.However, once disposed at a desired location (for example, as agenerally hemispherical dab less than about 5 mm in diameter or a layerless than about 2 mm in thickness) the composition regains its viscouscharacteristics and will not run (i.e., drip or flow other gravitationalpull).

[0040] To impact a thixotropic effect to the composition, and yet allowadequate inorganic filler to be incorporated into the curablecomposition to result in a desired hardness for restoring teeth, fumedsilica is preferably incorporated at a concentration of about 30% to70%, more preferably 40% to 60%, and even more preferably about 50% to60%, by weight of the inorganic filler material. Generally, particles oflarger than 0.05 micron (e.g., about 0.05 to about 5 microns) make upthe balance of the inorganic fillers. In a preferred mode, a smallamount of the curable composition (for example, a generallyhemispherical dab less than about 5 mm in diameter or a layer less thanabout 2 mm in thickness) can be deposited on the roof of a Class Vhollow and yet the composition will not run.

[0041] Preferably, the inorganic filler portion is a mixture ofinorganic fillers of various particle size and chemical and physicalproperties to provide hardness and abrasion resistance. For example,barium aluminum silicate glass can be mixed with silicon dioxide, andglass beads of mean particle size of 0.2 to 1 micron can be mixed withglass beads of mean particle size of 0.01 to 0.1 micron. The amount ofinorganic fillers that can be incorporated into the curable compositionto result in a particular viscosity is affected by the particle sizedistribution of the filler. Generally, when larger particle size fillersare used, more filler can be incorporated into the curable composition.The ratio can be adjusted to incorporate the desired amount of inorganicfillers in the curable composition for a desired viscosity.

[0042] To produce a composition that can result in a cured product ofdesired mechanical characteristics, the weight ratio of the curableliquid resin portion to the inorganic filler portion is preferably lessthan 7:3, more preferably less than about 1:1, even more preferablyabout 3:10 to 1:1, and most preferably about 2:5 to 3:5.

[0043] In the curable liquid resin portion, the weight ratio of thepolymerizable binder resin to the polymerizable diluent monomer isselected so that the curable liquid portion has a viscosity of less than6,000 cps at 25° C. and such that the curable liquid resin portion whencombined with the inorganic filler portion results in a compositioninjectable by a syringe through the lumen of a needle such as ahypodermic needle (e.g. 24 gauge needle). Preferably, the weight ratioof the polymerizable binder resin to polymerizable diluent monomer isfrom about 3:1 to 1:2, more preferably from about 3:2 to 2:3.

[0044] The composition of the present invention can be cured by usingvisible light. Suitable light sources that can be used for curing thecompensation is known in art and available commercially. Generally, thepolymerization initiating system is added in a quantity sufficient topolymerize a layer of the composition disposed on a tooth in about a fewseconds (e.g. 10 seconds) of visible light exposure. Typically, thealpha diketone is added in an amount of about 0.05 to about 0.5 percentof the composition and the reducing amine is added in an amount of aboutone to five times that of the alpha diketone.

[0045] Optional ingredients, such as pigments, opacifiers, brighteningagents, and other substances effective for modifying the aestheticappeal or chemical or physical characteristics of the composition beforeor after curing can be included in the composition. Although it can bedone in a different way, generally, the composition is made by mixingthe binder resin and the diluent monomer before the addition of theinitiating system components. Subsequent to the addition of theinitiating system components, the inorganic fillers and the optional ofthe ingredients are added and mixed to form the curable composition.

[0046] Tables A and B are preferred embodiments illustrative of thecomposition of the present invention. In Tables A and B, OX-50 is asilanated fumed silica sold by DEGUSSA CORP. BA-30 is barium glass beadfiller sold by INDUSTRIAL CORP. GI-2811 is an ionomer resin sold byINDUSTRIAL CORP. The ingredient 077WD (8 p) is a negative expansionfiller sold by INDUSTRIAL CORP. TABLE A Formulation of Bond Bis GMA 310g HEMA 206 g OX-50 70 g BA-30 30 g GI-2811 25 g Camphoroquinone 1 gAmine* 3 g

[0047] TABLE B Formulation of Curable Composition for Restoration BisGMA 288 g TEGDMA 288 g OX-50 540 g BA-30 230 g 077WD(8 μ) 195 gCamphoroquinone 1 g Amine* 3 g

[0048] The formulations of TABLE A and TABLE B are given asillustrations only. Other polymerizable resins and diluent monomers, aswell as inorganic fillers and initiators, as previously disclosed, canbe used by a person skilled in the art based on the present disclosure.For example, all the inorganic fillers in TABLE A or TABLE B can bereplaced with a 5:1 mixture of silanated glass (e.g. silicon dioxide)beads of mean particle size of about 0.5 micron and silanated glassbeads of mean particle size of about 0.05 micron Alternatively,commercially available bonds can be used Also, for the curablecomposition for restoration, a thicker universal paste type compositematerial such as P-50 or Z-100 from 3M Co. can be diluted with a diluentsuch as HEMA or TEGDMA to the desired viscosity. Such a material,although not as preferred as the composition of TABLE B, can be used forrestoring teeth with the method of the present invention.

[0049] Method of Tooth Restoration

[0050] To restore a decayed area in a tooth, first, the tooth isprepared by removing the decayed area. Often only the decayed portionneed to be removed. However, if desired, for example, to provide moreroom for manipulation and inspection, healthy tooth structure less thanabout 4 times, preferably about 0.5 to 3 times the size of the decayedportion can be removed. More preferably, healthy tooth structure of only0.5 to 2 times the size of the decayed portion is removed so as topreserve more healthy tooth structure. Subsequently, the surface of thetooth to which the curable composition of the present invention is to bebonded to is coated with a bonding composition (i.e. bond) such as oneshown in Table A. Generally, it helps the binder resin (and therefore acurable composition) to bind to the tooth.

[0051] Unlike restoration using amalgam which requires bulk to securethe amalgam in place, only a small amount of healthy tooth tissue needbe removed along with the decayed portion for receiving the compositionof the present invention. Although a large amount of healthy toothtissue can be removed, preferably, the amount of healthy tooth tissueremoved is one to three times the size of the decayed portion. Forexample, when removing the decayed portion one cubic millimeter of toothis removed, to prepare the tooth for receiving the curable composition,only an additional one to three cubic millimeter of healthy toothstructure adjacent to the decayed portion is removed. Furthermore, inremoving tooth structure to prepare for receiving the curablecomposition of the present invention, unlike using amalgam or thicksemisolid, conventional composite material, it is not necessary tocreate a hollow of excessively irregular shape or having a large openingleading into an even larger internal volume of hollow.

[0052] After a hollow has been prepared on the tooth to receive thecomposition, the surface of the tooth in the hollow is prepared byetching with a suitable etching solution such as a 10-35 weight percentphosphoric acid. Such etching procedures are known in the art. Theetched surface of the tooth is then washed, dried and coated with abond, which is then cured. These steps, including the application of thebond and the curing thereof can be done with conventional procedures. Abond such as “SCOTCHBOND™” sold by 3M Co. can be used. However, becauseof the better chemical and physical compatibility with the restorativecurable composition of the present invention, the bond of Table A ispreferred. Referring to FIG. 1, a curable composition of the presentinvention can be applied by using an applicator 1 with a needle liketubular structure, e.g., a conventional syringe 4 with a hypodermicneedle (for example, a bent 24 gauge lour-lock needle 6 for deliveryonto the tooth. Preferably the needle has a bend to facilitate deliveryof the composition around a corner. However, needles of other size canalso be used (e.g. 25 gauge to 16 gauge), depending on the preference ofthe operator (i.e., dentist).

[0053] The composition (preferably a thixotropic composition) ispreferably delivered as a thin layer 8 (i.e., less than 2 mm thick) or adrop (preferably less than five millimeter in diameter) on the bond 10in the hollow 12 which is on the occlusal side 13 opposite the gum 14.Because of the infinity of the bond 10 for the binder resins in thecomposition, the composition penetrates crevices and corners 16A, 16Breadily. Furthermore, the compensation can be manipulated by the tip 18of the needle 6 to spread out in the hollow or to achieve a specificdesire to shape.

[0054] If the hollow 12 is large, more than one layer 8 or drop of thecomposition may have to be applied. Before the application of anotherlayer or drop of the composition, the first layer or drop is cured by aradiation with a suitable light source (not shown).

[0055] Referring to FIG. 2, after curing, it is possible that the firstlayer or drop of composition might have shrunk a little. If thishappens, when a second layer or drop of the composition is applied, itis applied or spread to cover the edge 20 of the first layer 8 or dropso that any crevice or void 22 formed by the shrinkage of the firstlayer is filled. The second layer or drop of the composition is thencured. This process is repeated until the hollow in the tooth iscompletely filled and the composition manipulated or shaped to achieve adesired shape on the tooth (see FIG. 3). Shaping of the composition bylaying the composition and manipulating with a tip of the needle ispossible because the viscosity of the composition before curing is suchthat when applied in a volume as described above, the composition canmaintain a shape against the pull of gravity.

[0056] Generally, the outermost layer 26 of the composition on the tooth7 is shaped so that it conforms to the shape of the tooth and such thatits surface 28 is smooth. Typically, after curing, the surface 28 oftherestorative material is smooth and does not require polishing.

[0057] However, if desired, the surface of the restorative materialafter curing can be polished and glazed to result in a smooth surface.For example, if for any reason (such as overfilling by mistake) thesurface of the restorative material needs to be polished, afterpolishing, the surface is cleaned, etched with an etching solution,washed and dried. A small amount of the composition can be placed on theaffected area, brushed to obtain a smooth surface and cured. If there isany voids, porosities, shrinkage areas, or gaps in the margin (i.e. thearea between the restorative material and the tooth), they can be filledand sealed with the composition as described to obtain a smooth surface.Because of the presence of a substantial amount of the inorganic fillermaterial, the cured glaze (i.e. composition) in the method of thepresent invention, unlike prior art bonds and sealants, is veryabrasion-resistant.

[0058] The following examples illustrate the application of thecomposition and methods of the present invention in the restoration ofdefects in teeth.

EXAMPLE 1

[0059] The composition according to Table B was applied to a tooth as asealant. The occlusal pits and grooves of the tooth were slightlymanipulated with a rotating diamond instrument to clean the tooth andincrease the surface area. The surface of the tooth to be sealed wasthen prepared with a phosphoric acid solution. After etching, thephosphoric acid was washed from the tooth and the tooth was dried andcoated with the bond according to Table A by brushing. The compositionaccording to Table B was applied by means of a syringe through a 24gauge needle having a bent body without a sharp point (as shown inFIG. 1) into the pits and grooves of the tooth. The composition was thencured by a radiation with a visible light source (e.g., light of 484nanometer wavelength from a halogen light source). Referring to FIG. 4,a smooth layer of sealing coating 24 was formed on the tooth 27 coveringthe grooves 28 and crevices (not shown).

EXAMPLE 2

[0060] A Class I restoration was done with a composition according toTable B. The area of the caries in the tooth was removed until healthytooth structure was exposed without any decayed structure remainingthereon. At this point, no further amount of healthy tooth structure wasremoved. The occlusal surface of the tooth was then prepared as inExample 1 with etching and coating with the bond. The compositionaccording to Table B was then applied using a syringe with a 24-gaugeneedle similar to that of Example 1 so that the composition flowed intothe prepared area to fill the pits and grooves as well as the area wherethe caries had been. Referring to FIG. 5, the amount of filling material32 was small compared to the tooth 37.

EXAMPLE 3

[0061] The composition according to Table B was used to restore a ClassII cavity. The decayed area of the tooth was removed so that the toothstructure was exposed without any decay structure remaining at thispoint, no further healthy tooth structure was removed. There was no needto extend the-preparation margins (i.e., the margins of tooth structuralremoval) to the lingual and buccal aspects of the tooth to provide roomfor placement of restorative material and for visual inspection of thefinished restoration. After the removal of decayed structure, the toothwas further prepared by etching and the application of a bond in amanner similar to Examples 1 and 2. The composition according to Table Bwas applied by a syringe through a 24-gauge needle similar to that ofExample 1 into the hollow resulting from the removal of decayedstructure. A thin layer (less than two millimeter thick) of thecomposition was layered on the surface at the bottom of the hollow. Thecomposition was manipulated with the tip of the needle to spread thecomposition into any crevice or corner in the hollow. The thin layer ofcompensation was then cured by irradiation with visible light in amanner similar to the above examples. Subsequently a thin layer of thecomposition was applied on top of the first layered and manipulated withthe tip of the needle so that any groove or crevice in the hollow orresulting from shrinkage of the first layer was filled with thecomposition. The second layer was then cured by radiation with visiblelight. This process of laying and curing by a radiation was repeateduntil the hollow in the tooth was completely filled. The layersweremanipulated before curing so that the restorative structure had adesired shape conforming to the original shape of the tooth. Referringto FIG. 6, the filling 45 was disposed on the occlusal side 43 of thetooth 47 opposite the gum 14. The amount of filling material was smallcompared to the tooth.

EXAMPLE 4

[0062] The composition of Table B was used to repair a Class III cavity.The decayed area in the tooth was removed, etched and coated with a bondin a manner similar to the above examples. The composition of Table Bwas layered and cured in the hollow using a 24-gauge needle similar tothat of Example 1 in a manner similar to Example 3. However, becausegravitational force tends to pull the composition downward, the layeringwas done to gradually build up the restorative structure without thecomposition running out of the hollow to result in a shape that requiresremoval of excessive restorative material by abrasion after curing.Referring to FIG. 7, the amount of filling material 52 was smallcompared to the tooth 57.

EXAMPLE 5

[0063] The composition according to Table B was used to restore a ClassIV defect. The tooth was prepared by removing decayed structure, etchingand coating with a bond in a manner similar to the above examples. Athin layer of the composition according to Table B was applied to theprepared surface of the tooth by using a syringe and a 24 gauge needlesimilar to that of Example 1 and cured. Subsequently, additional layersof the composition were applied to the tooth, shaped by manipulationwith the syringe needle, and cured by exposure to visible light so thatthe final restorative structure conformed to the shape of the originaltooth. During the restorative procedure, some of the composition wasapplied as thin layers and some as small drops so that a desired shapewas achieved. Referring to FIG. 8, the amount of filling material 62 wasabout 30% the volume of the normally shaped tooth 67.

EXAMPLE 6

[0064] The composition according to Table B was used for restoring aClass V defect. The decayed tooth structure was removed, etched andcoated with a bond in a manner analogous to the above examples. Thinlayers or beads of the shaped composition according to Table B were laidusing a syringe with a 24 gauge needle similar to that of Example 1,shaped and cured by exposure to visible light one at a time until thehollow was filled and a desired shape conforming to the original shapeof the tooth was formed. The composition according to Table B wasapplied as a dab (or drop) on the bottom (i.e. upwardly facing) surfaceof the hollow. Because of its thixotropic nature, the composition willnot drip or run out of the hollow. The drop of the composition was thencured by exposure to visible light in a manner similar to the aboveexamples. Subsequently, another drop of the composition was placed inthe hollow adjacent to the first drop and cured. The process wasrepeated by building up the restorative structure without leavingunfilled space in the hollow or the composition running out of thehollow. The restorative structure was shaped by manipulating the dropswith the-needle in appropriate locations in the hollow to result in alateral surface that conforms to the surface of the original tooth. FIG.9 shows the cured drops 72 of the composition in the hollow of the tooth77.

[0065] The present invention has been described in the foregoingspecification. The embodiments are presented for illustrative purposesand are not to be interpreted as unduly limiting the scope of theinvention. It is to be understood that modifications and alterations ofthe invention, especially in size and structure or in substitution ofsimilar ingredients in the composition, will be apparent to thoseskilled in the art without departing from the spirit in scope of theinvention. For example, instead of utilizing photosensitive initiatorsfor curing the polymerization of the composition, initiators that causepolymerization without the presence of light can be used. Furthermore,instead of using a syringes, other means of forcing a thixotropiccomposition through a needle-type lumen can be used. Also, instead of aconstant-diameter hypodermic-needle-like instrument, an instrument witha small diameter needle-like tube at an end thereof for position of thecomposition may be used. All proportions and percentages describedherein are in weight unless specified otherwise.

What is claimed is:
 1. A method of restoring a tooth, comprising: (a)dispensing a curable composition from an applicator having a needle witha lumen into a hollow on the tooth to achieve a desired shape, thecomposition comprising: (i) curable liquid resin portion having apolymerizable binder resin; and (ii) inorganic filler portion; and (b)curing the curable composition.
 2. The method according to claim 1wherein the polymerizable binder resin is2,2-bis[4(2-hydroxy-3-methacryloxypropoxy)phenyl]propane.
 3. The methodaccording to claim 1 wherein the inorganic filer portion contains afiller selected from the group consisting of silica, barium aluminumsilicate, quartz, and silanated products thereof.
 4. The methodaccording to claim 1 wherein the curable composition further comprisesan initiator of polymerization and is visible light-curable.
 5. Themethod according to claim 1 wherein the curable composition isthixotropic.
 6. The method according to claim 1 wherein the dispensedcurable composition forms a cured restorative structure of desired shapeand smoothness upon curing.
 7. The method according to claim 1 whereinthe applicator is a syringe and the needle is a syringe needle.
 8. Themethod according to claim 1 further comprising a step of repeating thedispensing and curing steps to achieve a cured restorative structure ofa desired shape on the tooth.
 9. The method according to claim 1 furthercomprising a step of preparing the tooth to receive the curablecomposition by coating the hollow with a bond having a polymerizablebinder resin and a polymerizable diluent monomer less viscous than thepolymerizable binder resin.
 10. The method according to claim 1 whereinthe weight ratio of the curable liquid resin portion to the inorganicfiller portion is 3:10 to 1:1.
 11. The method according to claim 1wherein the weight ratio of the curable liquid resin portion to theinorganic filler portion is 2:5 to 3:5.
 12. The method according toclaim 1 wherein the curable liquid resin portion has a viscosity at 25°C. of from 500 to 5000 cps and wherein when a bead of the curablecomposition is deposited on a flat surface of a cured specimen of thecurable composition the bead will not run.
 13. The method according toclaim 1 wherein the curable liquid resin portion comprises apolymerizable binder resin and a polymerizable diluent monomer lessviscous than the polymerizable binder resin.
 14. The method according toclaim 13 wherein the diluent monomer is 2-hydroxyethylmethacrylate. 15.The method according to claim 13 wherein the diluent monomer istriethylene glycol dimethacrylate.
 16. The method according to claim 13wherein the weight ratio of polymerizable binder resin to polymerizablediluent monomer is from 3:1 to 1:2.
 17. The method according to claim 13wherein the weight ratio of polymerizable binder resin to polymerizablediluent monomer is from 3:2 to 2:3.
 18. A method of restoring a toothhaving a decayed portion, comprising: (a) removing the decayed portionand adjacent healthy portion of the tooth to form a hollow on the toothwherein the volume of the healthy portion removed is 0.5 to 3 times thesize of the decayed portion. (b) coating the surface in the hollow witha curable bond and curing the bond; (c) dispensing a curable compositionfrom an applicator having a needle with a lumen into the hollow toachieve a desired shape, the composition comprising: (i) curable liquidresin portion having polymerizable binder resin and polymerizablediluent monomer less viscous than the polymerizable binder resin; and(ii) inorganic filler portion; (d) curing the curable composition; and(e) repeating steps (c) and (d) until a cured structure of desired shapeand smoothness is obtained.
 19. The method according to claim 18 whereinthe hollow has walls generally divergently directing outward from theinterior of the hollow.
 20. The method according to claim 18 wherein inat least one of the dispensing steps, the curable composition is laid asa layer of less than 2 mm thick in the hollow before curing.
 21. Themethod according to claim 18 wherein steps (c) and (d) are repeated atleast 3 times.
 22. A method of restoring a tooth, comprising: (a)dispensing a curable composition from an applicator having a needle witha lumen in the form of one of a layer and a drop into a hollow on thetooth, the composition comprising: (i) curable liquid resin portionhaving polymerizable binder resin; and (ii) inorganic filler portion;(b) curing the curable composition, wherein the curable compositionshrinks during curing; (c) dispensing the curable composition from theneedle on the cured composition to further fill the hollow and tocompensate for the shrinkage to achieve a desired shape; (d) curing thecurable composition; and (e) repeating steps (c) and (d) until a curedstructure of desired shape is formed.
 23. A method of restoring a toothhaving a decayed portion, comprising: (a) removing the decayed portionand adjacent healthy portion of the tooth to form a hollow on the toothwherein the volume of the healthy portion removed is 0.5 to 3 times thesize of the decayed portion. (b) coating the surface in the hollow witha curable bond and curing the bond; (c) dispensing a curable,thixotropic composition from a syringe with a needle having a lumen intothe hollow to result in a desired shape of the curable composition, thecomposition comprising: (i) curable liquid resin portion havingpolymerizable binder-resin including2,2-bis[4(2hydroxy-3-methacryloxypropoxy)phenyl]propane and a diluentmonomer selected from the group consisting of 2-hydroxyethylmethacrylateand triethylene glycol dimethacrylate, the weight ratio of polymerizablebinder resin to polymerizable diluent monomer is from 3:1 to 1:2; and(ii) inorganic filler portion containing silica; wherein the viscosityof the curable liquid resin portion at 25° C. is 1000 to 6000 cps andthe weight ratio of curable liquid resin portion to inorganic fillerportion is 2:5 to 3:5 (d) curing the curable composition with visiblelight, wherein the curable composition shrinks during curing; (e)dispensing the curable composition from the needle on the curedcomposition to further fill the hollow and to compensate for theshrinkage to achieve. desired shape; (f) curing the curable composition;and (g) repeating steps (e) and (f) until a cured structure of desiredshape is formed; wherein the cured structure has desired smoothnesswithout polishing.
 24. A curable, thixotropic composition injectablethrough a hypodermic needle for filling a hollow in the restoration of atooth, comprising: (a) a curable liquid resin portion having apolymerizable binder resin; and (b) an inorganic filler portionincluding fumed silica.